Liquid Precursor SnS Thin Film Formation for Solar Cells
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Solution Overview
Problem
Current methods for forming SnS thin films for solar cells are costly and prone to generating secondary phases, making them unsuitable for industrial-scale production and commercialization due to the use of toxic materials and inefficient processing techniques.
Innovation Solution
A non-vacuum process using a precursor liquid with a liquid Sn precursor material, such as Sn-ethyl hexanoate, and a liquid S precursor material, like DMSO, is employed, eliminating the need for a drying process and sulfurization, allowing for heat treatment in an inert atmosphere to form high-quality SnS thin films without secondary phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional non-vacuum process (sulfurization or selenization) is used to form SnS thin film, then the process can be simplified, but secondary phases (Sn2S3 or SnS2) are easily generated
Solution Approach 1:
The invention changes the chemical composition parameters of the precursor solution by incorporating organic compounds (such as dimethyl sulfoxide, DMSO) along with tin salt and sulfur source. This compositional modification allows the precursor to decompose and form pure SnS phase during heat treatment without generating secondary phases like Sn2S3 or SnS2, thus achieving both process simplicity and phase purity.
Solution Approach 2:
The organic compound (DMSO) acts as an intermediary substance that facilitates the formation of pure SnS. It serves as both a solvent and a sulfur source, and its decomposition during heat treatment helps control the sulfur release rate, preventing the formation of secondary phases while maintaining process simplicity.
2Ease of manufacture
If thermal evaporation process is used to form SnS thin film, then the process can be implemented, but the efficiency is relatively low
Solution Approach 1:
The invention replaces the thermal evaporation process (a physical vapor deposition method) with a solution-based spin coating method followed by heat treatment. This substitution uses chemical processes instead of mechanical/physical evaporation, enabling better control over film composition and structure, which results in higher solar cell efficiency while maintaining ease of manufacture.
3Productivity
If ALD process is used to form SnS thin film, then the efficiency is best, but the process is difficult to apply industrially
Solution Approach 1:
The invention uses a simple, low-cost solution-based process that can be easily implemented in industrial settings, replacing the complex and expensive ALD process. The precursor solution can be prepared inexpensively and applied using straightforward spin coating, making the process industrially viable while achieving competitive efficiency through optimized solution composition and heat treatment.
4Quantity of substance
If SnS thin film is formed to reduce material cost, then the cost is reduced, but the light-absorption coefficient is much larger than silicon requiring careful thickness control
Solution Approach 1:
The invention incorporates the sulfur source (DMSO) directly into the precursor solution before deposition. This preliminary incorporation ensures that sulfur is available during the heat treatment step, allowing the formation of stoichiometric SnS with controlled thickness in a single process step, eliminating the need for subsequent sulfurization and providing precise thickness control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the production of high-quality SnS thin films at a lower cost, reducing processing time and preventing oxidation, thus enhancing the efficiency and cost-effectiveness of solar cells while avoiding toxic materials.
Implementation Method 1
heat-treating the precursor film
Implementation Method 2
heat-treating the precursor film to form a chalcogen compound thin film
Implementation Method 3
manufacturing a precursor liquid including an Sn precursor material and an S precursor material... The Sn precursor material and the S precursor material are liquid materials
Data Source
AI summary
Disclosed is a method of forming a chalcogen compound thin film suitable for use in a light-absorption layer of a solar cell. The method includes manufacturing a precursor liquid including an Sn precursor material and an S precursor material, applying the precursor liquid to form a precursor film, and heat-treating the precursor film. The Sn precursor material and the S precursor material are liquid materials. The present invention provides a method of forming a chalcogen compound thin film using a liquid precursor material without a sulfurization process, thereby forming a high-quality SnS thin film at low cost using a process which is suitable for mass production. Further, the light-absorption layer is formed using a process which is suitable for mass production, thus enabling the manufacture of a solar cell including the chalcogen compound thin film at low cost.